Open the Settings app
Tap Phone
Tap Blocked Contacts
Tap Edit
Tap the red minus icon next to the contact
Tap Unblock
Or open Settings
Tap Messages
Tap Blocked Contacts
Tap Edit
Tap the red minus icon next to the contact
Tap Unblock
Or open Settings
Tap FaceTime
Tap Blocked Contacts
Tap Edit
Tap the red minus icon next to the contact
Tap Unblock